Herb Gt5.0

I have an 86 Mustang GT. I removed the smog pump and installed a smogpump eliminator . Removed the plumbing and installed the plugs on the back of the heads. Installed 21/2" H Pipe with new shorty headers. I jave a hesitation when accelerating. Wondering if I have a vacuum leak. Any input out there?

SN Certified TechnicianFounding Member

Removing the pollution control equipment from a 5.0 Mustang is a bad idea. All you have accomplished is to make the computer mad and spit codes. The pollution control equipment all shuts off at wide open throttle, so the HP losses from it on the car are 2-5 HP. The catalytic converters may soak a few more HP than that. None of the pollution control equipment reduces the HP enough to cost you a race in anything but professional drag strip competition. I seriously doubt that you will be in the final runoff on “Pinks”, so leave the smog equipment in place and make sure it is working correctly.

Know what does what before removing it. Remove or disable the wrong thing and the computer sets the check engine light and runs in "limp mode". Limp mode means reduced power and fuel economy.

If you removed the smog pump and still have catalytic converters, they will ultimately clog and fail.

Here's a book that will get you started with how the Ford electronic engine control or "computer" works.

It's about $20-$45 from Borders.com see http://www.amazon.com/ . Select books and then select search. Use the ISBN number (without dashes or spaces) to do a search

Use the ISBN number and your local library can get you a loaner copy for free. Only thing is you are limited to keeping the book for two weeks. It is very good, and I found it to be very helpful.

Remove any of the equipment and you will not pass a full smog check, cannot title the car in an area that does smog checks and have broken several federal laws. Granted that the Feds are short on people to check cars, but it is still Federal law.

"Why should I leave the smog equipment on if I live in an area that doesn't do smog inspections?"
What's good sauce for the goose is good sauce for the gander. I lived in Florida and had two smog pumps fail on two different 89 5.0 Mustangs. I replaced both of them, even though there was no emissions inspection. Why?

1.) It a federal law that requires emissions equipment to be in place and functional. I have no intention of breaking a law designed to protect my general health and wellbeing, even if I don't like it. I have respect for the rights and wellbeing of other people, and am not one of those whose nature is rebellion.

2.) Whatever imaginary "improvements" someone may strive for, there is very little evidence that the results of removing emissions results in a better car. I can achieve excellent results in performance with all the smog equipment in place and working properly. Maybe you can't, but that is no excuse for removing the emissions equipment. Look at the new 5.0 Mustangs – 281 cubic inches and 400+ flywheel HP with full emissions equipment with no aftermarket parts. That tells me that it is possible on a mass production car. It also shows that the guys that designed the engine knew what they were doing to achieve that goal.

3.) I like to breathe clean air, and working emissions equipment helps me do my part to make that possible. Los Angeles has breathable air even with millions of cars: Beijing, the capitol of China has some of the worst air in the world. Why – no emissions requirements for cars.

Dump the codes: Codes may be present even if the Check Engine Light (CEL) isn't on.

Dumping the computer diagnostic codes on 86-95 Mustangs

Revised 26-July-2011. Added need to make sure the clutch is pressed when dumping codes.

Codes may be present even if the check engine light hasn’t come on, so be sure to check for them.

Here's the way to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great. You watch the flashing test lamp or Check Engine Light and count the flashes.

Post the codes you get and I will post 86-93 model 5.0 Mustang specific code definitions and fixes. I do not have a complete listing for 94-95 model 5.0 Mustangs at this time.

Be sure to turn off the A/C, and put the transmission in neutral when dumping the codes. On a manual transmission car, be sure to press the clutch to the floor.
Fail to do this and you will generate a code 67 and not be able to dump the Engine Running codes.

If your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.

The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.

89 through 95 cars have a working Check Engine light. Watch it instead of using a test lamp.

The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.

WARNING!!! There is a single dark brown connector with a black/orange wire. It is the 12 volt power to the under the hood light. Do not jumper it to the computer test connector. If you do, you will damage the computer.

What to expect:
You should get a code 11 (two single flashes in succession). This says that the computer's internal workings are OK, and that the wiring to put the computer into diagnostic mode is good. No code 11 and you have some wiring problems. This is crucial: the same wire that provides the ground to dump the codes provides signal ground for the TPS, EGR, ACT and Map/Baro sensors. If it fails, you will have poor performance, economy and driveablity problems

Some codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.

Dumping the Engine Running codes: The procedure is the same, you start the engine with the test jumper in place. Be sure the A/C is off, and clutch (if present) is pressed to the floor, and the transmission is in neutral. You'll get an 11, then a 4 and the engine will speed up to do the EGR test. After the engine speed decreases back to idle, it will dump the engine running codes.

Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.

Your 86-88 5.0 won't have a working Check Engine Light, so you'll need a test light.
See AutoZone Part Number: 25886 , $10

Alternate methods:
For those who are intimidated by all the wires & connections, see Actron® for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Wal-Mart.

I have an 86 Mustang GT. I removed the smog pump and installed a smogpump eliminator . Removed the plumbing and installed the plugs on the back of the heads. Installed 21/2" H Pipe with new shorty headers. I jave a hesitation when accelerating. Wondering if I have a vacuum leak. Any input out there?

Removing the pollution control equipment from a 5.0 Mustang is a bad idea. All you have accomplished is to make the computer mad and spit codes. The pollution control equipment all shuts off at wide open throttle, so the HP losses from it on the car are 2-5 HP. The catalytic converters may soak a few more HP than that. None of the pollution control equipment reduces the HP enough to cost you a race in anything but professional drag strip competition. I seriously doubt that you will be in the final runoff on “Pinks”, so leave the smog equipment in place and make sure it is working correctly.

Know what does what before removing it. Remove or disable the wrong thing and the computer sets the check engine light and runs in "limp mode". Limp mode means reduced power and fuel economy.

If you removed the smog pump and still have catalytic converters, they will ultimately clog and fail.

Here's a book that will get you started with how the Ford electronic engine control or "computer" works.

It's about $20-$45 from Borders.com see http://www.amazon.com/ . Select books and then select search. Use the ISBN number (without dashes or spaces) to do a search

Use the ISBN number and your local library can get you a loaner copy for free. Only thing is you are limited to keeping the book for two weeks. It is very good, and I found it to be very helpful.

Remove any of the equipment and you will not pass a full smog check, cannot title the car in an area that does smog checks and have broken several federal laws. Granted that the Feds are short on people to check cars, but it is still Federal law.

"Why should I leave the smog equipment on if I live in an area that doesn't do smog inspections?"
What's good sauce for the goose is good sauce for the gander. I lived in Florida and had two smog pumps fail on two different 89 5.0 Mustangs. I replaced both of them, even though there was no emissions inspection. Why?

1.) It a federal law that requires emissions equipment to be in place and functional. I have no intention of breaking a law designed to protect my general health and wellbeing, even if I don't like it. I have respect for the rights and wellbeing of other people, and am not one of those whose nature is rebellion.

2.) Whatever imaginary "improvements" someone may strive for, there is very little evidence that the results of removing emissions results in a better car. I can achieve excellent results in performance with all the smog equipment in place and working properly. Maybe you can't, but that is no excuse for removing the emissions equipment. Look at the new 5.0 Mustangs – 281 cubic inches and 400+ flywheel HP with full emissions equipment with no aftermarket parts. That tells me that it is possible on a mass production car. It also shows that the guys that designed the engine knew what they were doing to achieve that goal.

3.) I like to breathe clean air, and working emissions equipment helps me do my part to make that possible. Los Angeles has breathable air even with millions of cars: Beijing, the capitol of China has some of the worst air in the world. Why – no emissions requirements for cars.

Dump the codes: Codes may be present even if the Check Engine Light (CEL) isn't on.

Dumping the computer diagnostic codes on 86-95 Mustangs

Revised 26-July-2011. Added need to make sure the clutch is pressed when dumping codes.

Codes may be present even if the check engine light hasn’t come on, so be sure to check for them.

Here's the way to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great. You watch the flashing test lamp or Check Engine Light and count the flashes.

Post the codes you get and I will post 86-93 model 5.0 Mustang specific code definitions and fixes. I do not have a complete listing for 94-95 model 5.0 Mustangs at this time.

Be sure to turn off the A/C, and put the transmission in neutral when dumping the codes. On a manual transmission car, be sure to press the clutch to the floor.
Fail to do this and you will generate a code 67 and not be able to dump the Engine Running codes.

If your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.

The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.

89 through 95 cars have a working Check Engine light. Watch it instead of using a test lamp.

The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.

WARNING!!! There is a single dark brown connector with a black/orange wire. It is the 12 volt power to the under the hood light. Do not jumper it to the computer test connector. If you do, you will damage the computer.

What to expect:
You should get a code 11 (two single flashes in succession). This says that the computer's internal workings are OK, and that the wiring to put the computer into diagnostic mode is good. No code 11 and you have some wiring problems. This is crucial: the same wire that provides the ground to dump the codes provides signal ground for the TPS, EGR, ACT and Map/Baro sensors. If it fails, you will have poor performance, economy and driveablity problems

Some codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.

Dumping the Engine Running codes: The procedure is the same, you start the engine with the test jumper in place. Be sure the A/C is off, and clutch (if present) is pressed to the floor, and the transmission is in neutral. You'll get an 11, then a 4 and the engine will speed up to do the EGR test. After the engine speed decreases back to idle, it will dump the engine running codes.

Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.

Your 86-88 5.0 won't have a working Check Engine Light, so you'll need a test light.
See AutoZone Part Number: 25886 , $10

Alternate methods:
For those who are intimidated by all the wires & connections, see Actron® for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Wal-Mart.